Page 173 of The Secret of Secrets

Kerble had said nothing to his colleagues. Nor had he mentioned the ambassador’s aberrant behavior—including her arrival to the embassy on foot and unescorted. Nagel is the most ethical person I’ve ever met, he reminded himself. She’s clearly caught up in something I don’t understand.

Considering the ambassador was now in custody, he thought it prudent to recover her private SUV, get it off the street, and store it in the embassy’s parking courtyard with the rest of the fleet. Kerble went to the security office and retrieved the emergency set of keys they kept for all embassy vehicles. Then he turned to a computer terminal to pull up the location of the concealed tracking device that existed in any vehicle that might carry the ambassador. Kerble knew the SUV was close by, since the ambassador had walked back to the residence, but using the GPS coordinates would save him precious time wandering the streets.

He waited a moment as the tracker was activated. When the blinking dot appeared on the map of Prague, Kerble stared in confusion. The vehicle was most definitely not parked nearby, as expected. Instead, it was parked three miles away…on the ridgeline above Folimanka Park.

Several stories underground, The Golěm strode across the SMES vault toward the twelve Cryofab tanks of liquid helium. The top of each massive flask terminated in a reinforced electronic bayonet and valve connected to an insulated pipe that fed the SMES. On the wall near the tanks glowed a control panel bearing a diagram of all twelve canisters and their various statuses.

By all appearances, the screen regulated the flow of helium to each canister. The Golěm had no idea how to use this panel, nor did he have any intention of trying. What he was planning required no subtlety. There was a very simple way to halt the flow of the supercooled liquid into the SMES.

He approached the first canister, a bulbous stainless-steel flask taller than he was. His clay-caked face reflected back at him. I am not a monster, he reminded himself, knowing his outer shell, like everyone’s, was a mirage that shrouded the truth within. I am her protector.

As expected, at the top of each tank beside the clutter of electronic connectors and valves, there was a manual cutoff—a handwheel valve that one could turn in emergencies to stop the flow of helium.

As simple as turning off a garden hose.

According to everything he had read, the slow chain reaction would begin as soon as the flow of helium was halted, causing the superconducting coils to begin to heat up, losing some of their conductivity, resisting the current…and commencing a deadly feedback loop.

Heat Resistance Heat Resistance Heat…

Once I close the valves, he estimated, I’ll have about twenty minutes.

After that time, the coils would heat up and reach critical temperature—the “quench limit” when all the liquid helium in the system would begin to boil…converting to gas. The Golěm pictured the quench vent above him, which was now sealed shut, and he imagined the rapidly expanding cloud of helium gas trying to escape safely in a geyser of icy helium vapor.

No longer possible, he thought. Today will be a different scenario.

The rapidly expanding gas cloud would find no escape and would begin applying enormous pressure to every square inch of this airtight chamber.

Including on the rupture disks.

The Golěm took a deep breath and surveyed the line of canisters. He could already imagine the pressure in the vault climbing…pressing out against the thick concrete walls…causing the rupture disks in each tank to fail. Very suddenly, there would be some twenty thousand liters of liquid helium exposed to open air.

The chain reaction would be instantaneous and unstoppable—a catastrophic expansion event—as violent and destructive as igniting a powerful warhead in this small space.

Chapter 108

As he descended, Langdon found himself wishing their escape through the retracting wall had led to daylight, rather than to a ramp that spiraled deeper into the earth. While it was logical that a bomb shelter would have a lower level—after all, the nuclear command centers at Cheyenne Mountain and Yamantau Mountain were both built under more than a thousand feet of solid granite—Langdon had hoped to be carrying the evidence they had gathered up and out of Threshold…not farther into it.

With luck, whoever had entered Threshold behind them was not a threat, but still Langdon and Katherine had wasted no time beginning their descent and putting distance between themselves and whoever was entering behind them. Having finally obtained the proof they needed, they now had to find their way out.

Spiraling deeper, they reached the bottom of the ramp just as a frightening sound materialized above them—the rapid staccato of hard-soled shoes on concrete, moving at an accelerated pace. This was no janitor.

“We need to go!” Langdon whispered.

At the base of the ramp, there was another retractable wall, identical to the one above. They hurried through it and found themselves in an eerie corridor that was approximately thirty feet long. In the dim light, the matte-black walls, ceilings, and floors gave off the aura more of a mausoleum than a tech facility.

“It’s a different world down here…” Katherine whispered.

Wherever they now were, Langdon estimated they had less than twenty seconds to find a place to hide. The spiral ramp had left him increasingly disoriented, and the exit at Crucifix Bastion felt farther away with every step. Being spotted way down here, Langdon now feared, would result in an alarm being sounded, making escape nearly impossible.

They jogged down the sepulchral hallway, passing a long window on their right, beyond which a sea of green and red pinpoint lights pulsed in the darkness. Langdon could just make out the silhouettes of dozens of massive computer racks housed inside a meshed cage.

“Faraday shielding…” Katherine whispered. “Those computers must be quantum.”

Langdon knew very little about quantum computers except that they required shielding from cosmic rays and other forms of radiation. Another reason why Threshold is underground?

As they passed the computer room entrance, Katherine never slowed, apparently sharing Langdon’s instinct not to trap themselves inside a literal metal cage.

The hallway took a sharp left, and as they rounded the corner, more soft lighting came on, illuminating a much longer section of similar black corridor.